Silver-zinc, nickel-zinc and oxygen(air)-zinc alkaline batteries have not, in heretofore known embodiments, satisfied the need of the battery industry to provide a secondary battery of these types suitable for use in powering electric vehicles and in applications of like demand. These applications require deep (65%) discharge-recharge cycling capacity in the order of 300 cycles or more, a figure of merit not attained in known zinc-containing secondary batteries.
The inability of previous zinc alkaline batteries to meet such cycling capability is believed to be based principally on limitations of their negative electrodes. Thus, zinc active material electrodes heretofore known fail to repetitively provide uniform surface adherence for zinc electroreduced from the solid zinc compound state or deposited thereon from the electrolyte. This observation of applicant is appreciated in some measure in Morrison U.S. Pat. No. Re. 13,174 wherein it is noted, as introduction to the invention therein, that electrodes not originally including zinc active material fail to retain zinc deposited thereon from alkaline electrolytes containing zinc on repetitive discharge-recharge cycling. While some improvement in short term cycling is noted in this reissue patent on pre-plating cadmium or silver on the electrode and amalgamating it to form a surface suitable to receive the zinc, it is reported that electrolyte need be employed with such modified electrode in quantity exceeding that necessary to do the work involved. In its solution to the problem, this reissue patent departs from such use of cadmium plating, stated to be impractical, and discloses a mechanical electrode structure involving multiple wire screens to provide a retention bed for zinc active material.